In this part of the paper we focus solely on the algorithm which is able to follow the serpentinization process itself. We assume that the reaction described by Eq. REF  is the dominant process for serpentinite production in the planetesimals and we take only this reaction into account when we calculate the heat released, following [1]}.
The planetesimal used in the model is made of seven components: silicate rocks are forsterite (Mg-rich olivine), enstatite (Mg pyroxen), hydrated rock (serpentinite), non-reactive solid material and H2O in the three-phase state: liquid, solid and void space filled with H2O vapor.
The melting point of H2O (268 K) is obtained from the properties of a saturated solution of MgSO4 [2]}, which was used in model in earlier studies, too [3]}, [1]}. While MgSO4 is quite common in some chondrites [5]} in the case of TNOs other solutes could also be considered. However, the effect of any salt or salt combination on the melting temperature of water is probably small.
